SSHReverseTunnel Class

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The SSHReverseTunnel class provides a simple way to establish a reverse tunnel with a SSH host.

Syntax

class ipworksssh.SSHReverseTunnel

Remarks

The SSHReverseTunnel class may be used to establish a reverse tunnel with a SSH host. The SSH host will listen for incoming connections on the specified port and forward traffic to the class through the SSH tunnel.

The ssh_host and ssh_port properties specify the SSH server to use. The ssh_user and ssh_password properties allow the client to authenticate itself with the server. The on_ssh_server_authentication event and/or ssh_accept_server_host_key property allow you to check the server identity. Finally, the on_ssh_status event provides information about the SSH handshake.

To begin call ssh_logon to connect to the SSH host. After this method returns the connection to the SSH server has been successfully established. To establish a reverse tunnel call request_forwarding. This method takes parameters to tell the SSH host on which port to listen.

The class has two modes that allow data to be dealt with directly from the events, or automatically forwarded on to a different endpoint.

Event Based Operation

In this mode any data received by the class over the tunnel causes the events of the class to fire. For instance:

SSHReverseTunnel.RequestForwarding("0.0.0.0",777,"",0);

In the above code forwarding is request from port 777 on the ssh_host. Any data received on port 777 by the ssh_host will be sent to the class. In the above code the last two parameters are empty or 0 indicating to the class that no local forwarding is requested.

Once request_forwarding returns the SSH reverse tunnel is established and any connection made to the SSH host on the specified port will trigger events of the class to fire allowing you to handle the connection request and data.

When a client connects to the SSH host on the specified port the on_ssh_channel_open_request event will fire. Within this event choose to accept or reject the connection by setting the e.Accept parameter. This event contains details about the connection that may be used when determining whether to accept the connection.

After the channel is established data is received through the on_ssh_channel_data event. To send data over the channel call the send_channel_data method. To close the channel call the close_channel method.

Local Forwarding

In this mode the any data received by the class is automatically forwarded to a separate endpoint. This allows the class to act as a sort of proxy. There is no need to handle data directly in this case. For instance:

SSHReverseTunnel.RequestForwarding("0.0.0.0",777,"nsoftware.com",80);

In the above code forwarding is request from port 777 on ssh_host. The class is instructed to establish a connection to "nsoftware.com" on port 80 when a client connect to ssh_host on port 777. Any data received from the client connected to ssh_host on port 777 will automatically be forwarded to "nsoftware.com" on port 80. Any data received back from "nsoftware.com" on port 80 will be sent back to the connected client.

In this mode data may flow freely from the client connected to the ssh_host to the endpoint specified in the request_forwarding method without any additional code required.

Additional Notes

The following events are applicable when a connection is made to the SSH host:

• on_ssh_channel_closed
• on_ssh_channel_data
• on_ssh_channel_eof
• on_ssh_channel_opened
• on_ssh_channel_open_request
• on_ssh_channel_ready_to_send
• on_ssh_channel_requested

To stop a previously established reverse tunnel call the cancel_forwarding method.